The present invention relates to a curable epoxy composition and a substrate coated with the curable epoxy composition. The epoxy composition comprises an epoxy resin having at least 1.5 epoxy groups per molecule and an amine-terminated polyamide, preferably a liquid amine-terminated polyamide.
A typical commercial ambient-cure epoxy coating contains condensates of dimerized fatty acids (dimer acids) with polyethylene polyamines containing four or more amine hydrogens as a curing agent and a solution of a solid epoxy resin. This type of epoxy coating has excellent flexibility, good adhesion to many substrates, and good resistance to water and many types of solvents. As a result, these coatings find many applications in areas such as chemically resistant coatings, aesthetic topcoats, secondary containment membranes, films and others. However, such a system generally requires an organic solvent content of almost 50% in order to obtain a sprayable formulation with a Gardner D or lower viscosity. After application or use, the bulk of this organic solvent evaporates into the atmosphere as volatile organic compound (VOC). VOC""s are believed to cause adverse effects environmentally. Therefore, it is desirable and advantageous to reduce the required organic solvent content as much as possible in order to reduce the VOC content.
One way the organic solvent requirement can be reduced considerably is to use a system based on a liquid epoxy resin and the same polyethylenepolyamine curing agents. However, this approach tends to lead to coatings with lower flexibility. Accordingly, it is one object of the present invention to provide a curable epoxy coating system that has good or better flexibility with liquid epoxy resin and/or solid epoxy resin having reduced or comparable solvent requirements.
It is another object of the present invention to have a method for preparing a curable epoxy composition that is useful for various applications in coatings, secondary containment membranes, films or others, wherein the finished product has good tensile elongation property with no or only minimal adverse impacts on the tensile or tear strength over a wide curing agent-to-epoxy resin ratio.
It is a further object to prepare or provide articles, membranes, secondary containment membranes, films, topcoats or substrates coated with a cured composition. Curing may be carried out under effective conditions during and/or after the application of the epoxy coating.